Tear strength of rubber compositions is one of several properties that can take on significant importance when those rubber compositions are used in tires. The stresses placed on tires during long-term operation can cause fatigue fracture and may lead to crack formation and growth. Certain types of tires including off road and heavy truck tires are often subjected to particularly harsh conditions producing repeated, localized stresses on the tires. Such degradation of a tire is also referred to as chipping or chunking and it is most likely to occur at the tread surface, the underlying base material, or both. Resistance to this chipping or chunking has been referred to as tear strength or tear resistance.
Various attempts have been made to prevent or at least decrease this degradation (or to improve the tear strength of the rubber composition used in tires), including addition of reinforcing fillers such as carbon black, silica, or short fibers to the rubber compositions. Another attempt that has been employed is the addition of polyolefin (e.g., polyethylene, or polypropylene) to the rubber composition.